Loader bucket linkage



March 10, 1970 E. B. WAGNER LOADER BUCKET LINKAGE Filed Oct. 9, 1968 iNVENTOR. EDDIE B. WAGNER ffi''ofney United States Patent 3,499,566 LOADER BUCKET LINKAGE Eddie B. Wagner, Portland, 0reg., assignor to Wagner Mining Scoop, Inc., Portland, 0reg., a corporation of Oregon Filed Oct. 9, 1968, Ser. No. 766,111 Int. Cl. E0213 3/36, 3/70 US. Cl. 214-775 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to an improved linkage for leveling and tilting a bucket on the boom of a loader. The invention involves certain improvements over the linkage covered in the US. patent to Wagner 3,291,330.

As the term is used in the art, a loader is a vehicle having a bucket on the end of a forwardly extending boom. The bucket is used as a scoop by tilting it forward and lowering the boom while driving the vehicle forward to shovel material into the bucket. For carrying the load, the boom is raised slightly so that the bucket will clear the ground and the bucket is turned upright on the boom to contain the load. The bucket is dumped by tilting it forward with the boom either raised or lowered.

A problem arises in providing a linkage which will tilt the bucket far enough forward to dump its load when the boom is raised as in loading a truck, particularly when a simple form of linkage is employed mounted directly over the boom. Prior linkages arranged to dump a bucket in a high boom position have been excessively complicated and expensive.

My prior Patent No. 3,291,330 discloses a bucket linkage having a joint which will break in one direction to pivot the bucket forward as far as necessary to dump the bucket when the boom is raised and the linkage is under tension. The joint embodies a novel locking device which rigidifies the linkage so that the joint will not break when the linkage is straightened out and under compression. Such a joint permits a linkage of relatively simple and economical construction placed directly above the boom so that the linkage will automatically level the bucket as the boom is raised and lowered.

Objects of the present invention are to provide an improved bucket linkage of the type shown in Patent 3,291,330, to provide means for jarring a heaped up load to the back of the bucket when the bucket is erected to carrying position after scooping so that the load will not spill while the vehicle is traveling, and to provide a novel arrangement of stops for arresting the rotative movement of the bucket when it is erected.

SUMMARY OF THE INVENTION bucket. The bucket is tilted forward on its boom for scooping and dumping by extending the piston rod and it is erected for carrying a load by retracting the piston rod. After scooping up a load of material, the retracting movement of the piston rod is arrested rather gently by the action of the hydraulic system leaving the load heaped up in the front side of the bucket and leaving the back side of the bucket incompletely filled. This results in considerable spillage when the vehicle travels over rough ground with its load.

In the present construction a stop is provided on the boom to limit the downward swinging movement of the piston rod in erecting the bucket and a stop is provided on the back of the bucket to engage the link interconnecting the piston rod and bucket when the bucket reaches the erected position. The novel relationship of these two stops abruptly halts the erecting movement of the bucket, jarring the heaped up portion of the load to the partially empty back part of the bucket. This levels the load sufliciently that spillage is substantially eliminated in traveling on rough ground.

The foregoing and other objects and advantages will become apparent and the invention will be better understood from the following description of the preferred embodiment illustrated on the accompanying drawing. Various changes may be made, however, in the details of construction and arrangement of parts and certain features may be used without others. All such modifications are included in the invention.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a side elevation view of the front end of a loader vehicle showing its boom and bucket in different positions in full and broken lines;

FIGURE 2 is a view taken approximately on the line 22 in FIGURE 1;

FIGURE 3 is an enlarged view on the line 3-3 in FIGURE 2; and

FIGURE 4 is a schematic diagram illustrating the geometry of the linkage.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present boom and bucket linkage may be mounted on various types of loader vehicles. For purpose of illustration, FIGURE 1 shows the front end of such a vehicle having a frame 10 and front wheels 11. The rear end of the vehicle is supported on a similar pair of wheels and carries an engine for driving the vehicle. Associated with the engine is a hydraulic pressure system for operating various instrumentalities by means of suitable control valves at the operators station.

A forwardly extending boom 12 is pivotally mounted at its rear end on pins 13 in frame 10. The front end of the boom is forked, having a pair of arms 14 straddling opposite sides of loader bucket 15. A pair of pins 16 in the arms 14 provide pivotal support for the bucket on the boom. The boom is raised and lowered by a pair of boom liftcylinders 17 having piston rods 18 on opposite sides of the boom. The lower ends of cylinders 17 are pivotally connected to frame 10 by means of pins 19 and the upper ends of piston rods 18 are pivotally connected to the boom by means of pins 20.

Bucket 15 is tilted on its supporting pins 16 by a linkage comprising a double acting cylinder 25, piston rod 26 and link 27. The rear end of cylinder 25 is pivotally connected to frame 10 by a pin 28. The front end of piston rod 26 is pivotally connected to the rear end of link 27 by a pin 30 and the front end of link 27 is pivotally connected by a pin 31 with an ear 32 on the back wall 33 3 of the bucket. The bucket also has a pair of opposite end walls 34 which support the bucket on pins 16 and a front wall 35 with a lip 36 on its upper edge for digging and scooping.

Cylinder 25, piston rod 26 and link 27 form one arm of a parallelogram linkage which holds the bucket erect when the boom is raised.

Link 27 has a rear end portion 40 of inverted U-shape extending behind pin 30 and overhanging piston rod 26. In certain positions of the boom and bucket where the swinging movement of the piston rod 26 is unrestrained, the three pins 28, 30 and 31 lie in a straight line in FIG- URE 1 when the piston rod 26 and link 27 are under tension. When the piston rod and link are under compression, the joint at pin 30 drops by gravity to an over-center position slightly below a line interconnecting pins 28 and 31. In such position, extension 40 bears against the upper side of piston rod 26 to lock the joint against further pivotal movement so that linkage members 26 and 27 then function as a rigid compression or thrust member.

Thus, in the digging or scooping position of the bucket shown in broken lines at -15a, the piston rod at 26a and link at 27a have dropped into locked position by gravity, allowing these linkage members to exert thrust on the bucket for digging or scooping up material when the vehicle is driven forward. In the raised position of the boom and bucket at 12b and 15b, the link members 26b and 27b may be under compression or tension depending upon the balance of the bucket and its load on supporting pins 16. If the link members are under compression, that condition will be changed to tension loading as the bucket is tilted forward to its dumping position at 150. Link 27 then assumes a position wrapping around and bearing against a bottom portion of the bucket as shown at 270 with the link members 26c and 270 assuming an angular relation to each other. The bearing of link 270 against the bottom of the bucket provides a fulcrum for erecting the bucket from its dumping position when piston rod 26c is retracted.

Similarly, when the bucket is dumped in a low boom position, the linkage members 26 and 27 will be placed under tension as the bucket tilts forward but, in this case, dumping position is assumed before link 27 comes into contact with the bottom of the bucket. The low boom dumping position is not illustrated. The parts thus far described correspond quite closely with the linkage shown in Patent No. 3,291,330.

The principal features of novelty in the present construction comprise a pair of stops 45 and 46. Stop 46 is mounted on the back wall 33 of the bucket above pin 31 and extending rearwardly in overhanging position above link 27. This stop may be integral with ear 32 which carries the pin 31. Stop 45 is mounted on a bridge member 47 interconnecting the side plates 48 of boom 12 as shown in FIGURE 3. This stop is engageable With an eye 50 on the end of piston rod 26 which received the pin 30.

When the present bucket is erected from scooping position at 15a to carrying position at 15, the linkage members 26a and 27a do not continuously maintain a straight line relationship as in Patent No. 3,291,330. In said patent the erected or carrying position of the bucket is determined by the operator by manipulation of the valve which controls fluid flow to opposite ends of the double acting cylinder. By shifting its control valve to off position, the operat-or prevents hydraulic fluid flow to or from the opposite ends of the cylinder, stopping the retracting movement of the piston rod and hydraulically locking the piston rod in fixed position in the cylinder.

In the present construction the stops 45 and 46 mechanically stop the retracting movement of the bucket and linkage and the operator does not place the control valves in off position until after all movement has been stopped. In erecting the bucket from scooping position, cylinder 25 and piston rod 26 swing clockwise about pivot pin 28. It will be observed in FIGURE 4 that stop 45 arrests this downward movement before the extended axis 55 of the all) piston rod intersects the axis of bucket supporting pins 16. When piston rod eye 50 contacts stop 45, extended piston rod axis 55 is still at a distance above the axis of pins 16 as repersented by the dimension 56. At this instant, pin 31 is at point 31a.

As piston rod 26 continues to retract, eye 50 slides a short distance on stop 45, pulling pin 31 to its position indicated at 31. At this instant, stop 46 engages link 27 to abruptly arrest the counterclockwise pivotal movement of the bucket about its axis of rotation on pins 16. This jars the pile of material 60 adjacent the front wall of the bucket rearwardly towards the back wall 33, leveling off the top of the pile to a more even contour as indicated at 61. In this condition, the material does not spill out of the bucket during transportation.

The jarring effect just described is enhanced by the angular acceleration of the bucket as it approaches its erect or carrying position. In scooping position of the bucket, pin 31 is at position 31b in FIGURE 4 and at the beginning of the erecting movement, piston rod 26 is approximately tangential to the arc of travel 65 of pin 31 whereby this pin moves at approximately the same speed as the piston rod. A small increment of retraction of the piston rod produces a corresponding increment of arcuate movement of pin 31 to position 310 as represented by the dimension 66. For the purpose of comparison, this arcuate increment has been made equal to the arcuate increment 67 through which the pin travels from position 31a to position 31. But while pin 31 is moving a distance equal to the dimension 67, the piston rod is retracting the much shorter distance represented by the dimension 68.

If the hydraulic system is of sufficient capacity to retract the piston rod at approximately constant velocity, the rotation of the bucket accelerates continuously from its starting position at 31b to its terminal position at 31 at which point is rotation is halted abruptly by the joint action of stops 45 and 46. Then, the operator returns the valve controlling cylinder 25 to its off position, placing the piston rod 26 in hydraulic lock in the cylinder to hold the bucket in erect position. In this position the axes of the three pins 16, 30 and 31 are in alignment on the line 70 which is at an angle to the axis of piston rod 26.

When piston rod 26 is extended to tilt the bucket, link 27 bears against stop 46 to lift the rear side of the bucket until the bucket overbalances forward and places the link and piston rod in tension, straightening out the joint at pin 30. When the tension is relaxed, extension 40 locks the joint so that link 27 can operate as a thrust member for scooping.

When link 27 bears against stop 46 to lift the rear side of the bucket as described above, the link operates as a crank arm to increase the leverage of the piston rod on the bucket at the beginning of the movement. This feature makes possible the unusually large angle of pivotal movement of the bucket necessary for dumping in the high boom position without resorting to a complex and expensive type of linkage. It will be observed that the bucket swings through an arc of approximately relative to the boom in moving from its carrying position at 15 to its high dump position at 15c.

Stops 45 and 46 have the further advantage of mechanically and automatically determining the erect position of the bucket on the lowered boom without requiring the careful attention of the operator to this phase of the operation.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

1. A loader comprising a boom pivotally mounted for vertical movement, a bucket pivotally mounted on said boom, a linkage extending along said boom and connected with said bucket for pivoting the bucket to scooping, carrying and dumping positions, said linkage having a downward movement in erecting said bucket from scooping to carrying position, a stop on said boom under said linkage to limit said downward movement of said linkage, and a stop on said bucket engageable with the upper side of said linkage in said carrying position.

2. A loader as defined in claim 1, said linkage comprising a link pivotally connected with said bucket and a linkage member having pivotal connection with said link, said first stop being engageable with said last pivotal connection, and said second stop being engageable with said link.

3. A loader as defined in claim 2, said linkage member comprising a cylinder and piston rod.

4. A loader as defined in claim 2, said last pivotal connection having gravity actuated over-center stop means to lock said pivotal connection when said link and linkage member are brought into alignment.

5. A loader as defined in claim 2, said bucket having further pivotal movementon the boom after movement of said linkage is limited by said first stop and before said second stop engages said link.

6. A loader as defined in claim 1, said linkage forming one arm of a parallelogram linkage to hold the bucket erect when the boom is raised.

References Cited UNITED STATES PATENTS 3,291,330 12/1966 Wagner 214-140 HUGO O. SCHULZ, Primary Examiner US. Cl. X.R. 214-778 

